What is the initial treatment for a patient with wide complex tachycardia, particularly if they are hemodynamically unstable with symptoms such as chest pain, shortness of breath, or syncope?

Wide Complex Tachycardia: Initial Treatment

If the patient is hemodynamically unstable (presenting with chest pain, shortness of breath, syncope, altered mental status, hypotension, or shock), perform immediate synchronized cardioversion without delay. 1, 2

Immediate Assessment and Stabilization

Determine Hemodynamic Stability

• Unstable patients require immediate electrical cardioversion - this is a Class I recommendation with no exceptions for wide complex tachycardia presenting with severe symptoms 1, 2
• Signs of instability include: acute altered mental status, ischemic chest discomfort, acute heart failure, hypotension, or other signs of shock 1, 2
• Sedate the conscious patient prior to cardioversion if time permits, but do not delay the procedure 1

Critical Action Points for Unstable Patients

• Presume all unstable wide complex tachycardia is ventricular tachycardia and treat accordingly with immediate cardioversion 1, 2, 3
• A precordial thump may be considered only for witnessed, monitored unstable VT if a defibrillator is not immediately ready, but this should never delay definitive therapy 1
• Establish IV access, attach cardiac monitor, and provide supplemental oxygen, but do not delay cardioversion to obtain a 12-lead ECG 2

Management of Stable Wide Complex Tachycardia

Rhythm Classification

If the patient is stable, obtain a 12-lead ECG to determine if the rhythm is regular or irregular 1

For Regular Monomorphic Wide Complex Tachycardia:

• First-line pharmacologic options (if cardioversion not immediately needed):

  • Procainamide (Class IIa) for patients without severe CHF or acute MI 1
  • Amiodarone 150 mg IV over 10 minutes (Class IIb) - effective for both stable monomorphic VT with or without CHF/AMI 1, 4
  • Sotalol (Class IIb) may be considered, including in patients with AMI, but avoid in prolonged QT 1

• IV adenosine may be considered (Class IIb) if the rhythm is regular, monomorphic, and etiology cannot be determined - it is relatively safe for both treatment and diagnosis 1

For Irregular or Polymorphic Wide Complex Tachycardia:

• Never give adenosine - it may cause degeneration to ventricular fibrillation (Class III) 1
• If associated with prolonged QT: IV magnesium is the treatment of choice 1
• If no prolonged QT and ischemia suspected: IV amiodarone or β-blockers may reduce arrhythmia recurrence 1

Critical Contraindications and Pitfalls

Medications to Avoid

• Verapamil is absolutely contraindicated for wide complex tachycardia unless definitively known to be supraventricular in origin (Class III) 1
• Do not give adenosine for unstable, irregular, or polymorphic wide complex tachycardia (Class III) 1, 2
• Avoid procainamide and sotalol in prolonged QT 1
• Do not give a second antiarrhythmic agent without expert consultation if the first is unsuccessful 1

Common Clinical Errors

• Delaying cardioversion in unstable patients while attempting to obtain diagnostic studies is the most dangerous error 2
• Using AV nodal blocking agents (diltiazem, verapamil, β-blockers) in pre-excited atrial fibrillation can precipitate ventricular fibrillation 2
• Attempting to normalize heart rate when tachycardia is compensatory (e.g., hypovolemia, sepsis) rather than treating the underlying cause 2

Amiodarone Dosing (When Indicated)

Initial loading dose: 150 mg in 100 mL D5W infused over 10 minutes 4

• For breakthrough VF or unstable VT: Repeat 150 mg supplemental infusions over 10 minutes 4
• Maintenance infusion: 1 mg/min for 6 hours, then 0.5 mg/min thereafter 4
• Maximum daily dose: Do not exceed 2100 mg in first 24 hours due to increased hypotension risk 4
• Administration: Use volumetric infusion pump; concentrations >2 mg/mL require central venous catheter 4

Post-Cardioversion Management

• If cardioversion is unsuccessful or tachycardia recurs, consider antiarrhythmic medications based on specific rhythm 2
• For persistent hypotension after cardioversion, initiate vasopressor therapy with norepinephrine as first choice 2
• Expert consultation should be obtained for refractory cases 1